1. Field of the Invention
The present invention relates to a proximity sensor.
2. Description of the Related Art
As a position detecting apparatus for detecting the slide position of a seat for use in a vehicle, there is known an apparatus which uses a proximity sensor of a magnetic field detect type (see, JP-A-2006-281813 and JP-A-9-511357).
According to this position detect apparatus a member to be detected made of a magnetic member is provided on a lower rail to be fixedly installed on the floor of a vehicle body. A proximity sensor including a magnetic field generating portion (a permanent magnet) and a detect portion (a Hall IC) is provided on an upper rail formed integrally with the vehicle seat.
In this position detect apparatus, when the proximity sensor is moved according to the sliding movement of the vehicle seat, the magnetic field of the magnetic field generating portion to be detected by the detect portion is varied according to the position relationship between the proximity sensor and the member to be detected, and the slide position of the seat is detected based on the thus varied magnetic field.
However, in the above-mentioned related proximity sensor, when the relative position relationship between the housing of the proximity sensor and the detect portion thereof is shifted, the magnetic field of the magnetic field generating portion may be varied to thereby worsen the detect precision of the proximity sensor. In other words, when a distance from the detect portion of the proximity sensor to the member to be detected varies with age, there is a fear that the amount of variation of the magnetic field may be varied to thereby vary the slide detect position of the seat.